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/*
 *  streams library
 *
 *  Copyright (C) 2011-2014 by Christian Bockermann, Hendrik Blom
 * 
 *  streams is a library, API and runtime environment for processing high
 *  volume data streams. It is composed of three submodules "stream-api",
 *  "stream-core" and "stream-runtime".
 *
 *  The streams library (and its submodules) is free software: you can 
 *  redistribute it and/or modify it under the terms of the 
 *  GNU Affero General Public License as published by the Free Software 
 *  Foundation, either version 3 of the License, or (at your option) any 
 *  later version.
 *
 *  The stream.ai library (and its submodules) is distributed in the hope
 *  that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
 *  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package stream.io;

import java.io.InputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import stream.Data;
import stream.annotations.Parameter;
import stream.data.DataFactory;
import stream.data.SequenceID;

/**
 * @author Christian Bockermann, Hendrik Blom
 * 
 */
public abstract class AbstractStream implements Stream {
	static Logger log = LoggerFactory.getLogger(AbstractStream.class);

	protected SourceURL url;
	protected Long limit = new Long(-1L);
	protected Long count = new Long(0L);
	protected String prefix = null;
	protected String id;
	protected InputStream in;
	protected boolean closed = false;
	protected SequenceID seqId = new SequenceID();
	protected String sequenceKey = null;

	public AbstractStream(SourceURL url) {
		this.url = url;
	}

	public AbstractStream(InputStream in) {
		this.in = in;
	}

	protected AbstractStream() {
		this.url = null;
	}

	protected InputStream getInputStream() throws Exception {
		if (closed)
			throw new IllegalStateException("Stream must be closed first!");
		if (in == null) {
			in = url.openStream();
			return in;
		}

		return in;
	}

	public String getId() {
		return id;
	}

	@Parameter(required = true, description = "The ID of this stream for associating it with processes.")
	public void setId(String id) {
		this.id = id;
	}

	public SourceURL getUrl() {
		return url;
	}

	public void setUrl(SourceURL url) {
		this.url = url;
	}

	/**
	 * @return the prefix
	 */
	public String getPrefix() {
		return prefix;
	}

	/**
	 * @param prefix
	 *            the prefix to set
	 */
	@Parameter(required = false, description = "An optional prefix string to prepend to all attribute names.", defaultValue = "")
	public void setPrefix(String prefix) {
		this.prefix = prefix;
	}

	public Long getLimit() {
		return limit;
	}

	@Parameter(required = false, description = "The maximum number of items that this stream should deliver.", defaultValue = "-1", max = Long.MAX_VALUE)
	public void setLimit(Long limit) {
		this.limit = limit;
	}

	public String getSequenceKey() {
		return sequenceKey;
	}

	@Parameter(description = "An optional key which should contain a sequence ID for each item. If not specified, not sequence IDs will be generated.")
	public void setSequenceKey(String sequenceKey) {
		this.sequenceKey = sequenceKey;
	}

	/**
	 * @see stream.io.Stream#read()
	 */
	public synchronized Data read() throws Exception {

		if (closed || (limit > 0 && count >= limit))
			return null;

		Data datum = readNext();
		if (datum == null) {
			log.debug("End-of-stream reached!");
			return null;
		}

		if (this.id != null)
			datum.put(SOURCE_KEY, this.id);

		if (this.sequenceKey != null) {
			SequenceID next = this.seqId.getAndIncrement();
			datum.put(sequenceKey, next);
		}
		if (prefix != null && !prefix.trim().isEmpty()) {
			Data prefixed = DataFactory.create();
			for (String key : datum.keySet()) {
				prefixed.put(prefix + ":" + key, datum.get(key));
			}
			datum = prefixed;
		}
		count++;
		return datum;
	}

	public abstract Data readNext() throws Exception;

	/**
	 * @see stream.io.Source#init()
	 */
	@Override
	public void init() throws Exception {
		closed = false;
	}

	/**
	 * @see stream.io.Source#close()
	 */
	@Override
	public void close() throws Exception {
		if (in != null)
			in.close();
		in = null;

		closed = true;
	}
}